1. Field of the Invention
The present invention relates to a high frequency module for use with high frequency band, such as the microwave band or millimeter-wave band, applications, such as in a radar apparatus, communications apparatus, or other apparatus operating in a high frequency band.
2. Description of the Prior Art
FIG. 1 is a perspective view of a conventional high frequency module. FIG. 1 shows a metal chassis 1; a waveguide terminal 2 for carrying high frequency RF signals, such as microwave signals, along the substrate thickness of the chassis 1, to and from a waveguide (not shown in the figure) connected to the bottom surface of the chassis 1; a package 3 including a high frequency circuit; and connection lines 4 for carrying RF signals and consisting of a dielectric substrate formed with microstrip lines on the top surface. FIG. 2 shows the configuration of the package 3, with the right side a perspective view of the package 3 and the left side a perspective exploded view of the package. The package 3 comprises a carrier 5 provided underneath the package 3; dielectric substrates 6 mounted on the carrier 5; a feed-through terminal 7 for carrying RF signals between a high frequency circuit 9 and the connection line 4 and enabling the maintaining an airtight atmospheric integrity for the package 3; a seal 8 having a frame shape and made of metal; the high frequency circuit 9, such as a monolithic microwave IC (MMIC) or high frequency resistor; bias and control signal pins 10 for inputting and outputting DC signals from and to the high frequency circuit 9; and a metal cover 11 joined onto the top surface of the seal 8.
The configuration of such a conventional high frequency module will be described next. The conventional high frequency module shown in FIG. 1, comprises a plurality of packages 3, which are connected via connection lines 4, positioned on the chassis 1 having a plurality of the waveguide terminals 2. Furthermore, the package 3 has laminated onto the metal carrier 5 a plurality of the dielectric substrates 6, on which the feed-through terminal 7 and the seal 8 are positioned, in such a manner that a cavity is provided within the seal 8. In this cavity is mounted the high frequency circuit 9. A slot is provided in the side of the seal, and in this slot the feed-through is positioned and sealed so that RF signals can be communicated to and from the connection lines 4, while maintaining the atmospheric integrity inside the package 3. Furthermore, the connection lines 4 are connected to the waveguide terminals 2 to carry RF signals between the high frequency circuit 9 and the waveguide terminals 2. The RF signals carried from the connection lines 4 to the waveguide terminals 2 are carried within the waveguide terminals 2 in waveguide mode, and the bias and control signals to the high frequency circuit 9 are obtained via the bias and control signal pins 10 provided underneath the dielectric substrate 6. The cover 11 is then joined onto the seal 8 by soldering, adhesion, or resistance welding, to seal the package 3. However, because a plurality of packages 3 are positioned on the chassis 1 in this manner, the signal loss due to the connection lines 4 for connecting between the respective packages is large and the performance as a high frequency module degrades. Furthermore, when positioning the connection lines 4 on a chassis as large as the chassis 1 and connecting the packages 3 with the connection lines 4, connection is commonly performed by applying wire bonding using thermo-compression bonding, which introduces unfavorable assembly operations, such as, for example, the heating of the entire chassis 1 to a temperature of 150° C. for a long heating time, poor handling of the chassis 1, and so forth. Furthermore, even where a plurality of the packages 3 are used, cost reduction is difficult. Even when the plurality of packages have a common function, each package must still be individually equipped with that same function. In other words, a common function cannot be integrated, and cost can not be lowered through mass production. Therefore, conventional high frequency modules have problems such as performance degradation, unfavorable assembly operations, and high cost.
As described above, because conventional high frequency modules comprise a plurality of packages, problems include the degradation of characteristics in the connection lines; unfavorable assembly operations during mounting and connection of the connection lines; high cost; and so forth.